I don't know where the reference to Burnt Ends in Texas comes from, that is a KC thing mostly, with a little bit from the South. East Texas does have a chopped brisket tradition is a small regional area.
Most all of the modern Texas tradition (as I understand it) is about sliced brisket, ordering lean (flat) or fat (point). My cousin, from North Texas (go Panhandle State Aggies
, who knew there were rodeo scholarships?) said that brisket was supposed to be lean, and he always ordered the lean, the fat would make you weak.